Progress in the treatment of chronic, intractable pain has been limited by the lack of reliable, quantifiable measures of pain severity. Many types of chronic pain are exacerbated by movement. Capitalizing on the observation that mental motor imagery engages many of the same sensori-motor processes engaged by real movement, we have demonstrated in two preliminary investigations that performance on tasks that involve imagined movements is altered in a specific and reproducible fashion by chronic pain. Based on current accounts of the relationship between real and imagined movements as well as our studies to date, we argue that simulated action provides a measure of pain that is quantifiable, reproducible and responsive to therapeutic interventions. As the proposed tasks provide measures of performance (e.g., reaction times and accuracy) that reflect the integrity of the underlying sensori-motor processing, these tasks are expected to provide measures of pain severity that more directly reflect functional status than multiply-determined global measures of pain severity. Finally, as mental motor imagery tasks require minimal language capacity or abstract reasoning, we propose to investigate the use of these measures in subjects with cognitive impairment.